Agree that distances of 250 miles or less are the "happy medium" for passenger service. Very few business travelers from KC-Denver are going to sit for 8 or 10 hours while getting from one place to another.

That said, there may be markets within those end points. There's probably no fast way to get from Colorado Springs to Topeka - you either drive or put up with incovenient airline schedules involving multiple changes of plane, plus a rent-a-car.

On a related note, there may even be a market for LA-Bay Area overnight train service, but not via the old Lark routing. Given the population growth in the central valley, it might make more sense to go that way, provided congestion issues through Soledad Canyon and over Tehachapi could be addressed. A 6 PM departure from both ends with an 8 AM arrival would probably be about right for both through passengers and early AM commuters (high desert-LA and Stockton-Bay area).